The invention relates to the construction of a throttle valve for an internal combustion engine.
A throttle valve is disclosed in EP 624 228 B1 in which a throttle valve body is supported in a metering venturi passage in an intake channel for precisely controlling air flow in the intake channel, particularly at small opening angles of the throttle valve. The throttle valve body is not cylindrical but has an elliptical outer contour, such that the circumferential surface of the throttle valve body almost seals the intake channel when in a closed position at an inclination angle of about 3-15xc2x0.
Positioning of such an elliptical or oval throttle valve body so that its opposite elliptical edges engage the inside surface of the cylindrical intake channel in the closed position must be performed by hand, in order to achieve a uniform and minimum circumferential gap for passage of leakage air. Even a slight angular deviation of the throttle valve body from the optimal position leads to an undesired increase of the air flow. This is especially the case at idling, since the necessary lifting of the valve body in the opening direction must be relatively large, in order to prevent jamming and sticking of the valve body. Manual adjustment is time consuming and expensive, and makes automatic assembly of the throttle valve impossible.
An object of the invention is to provide a throttle valve which does not suffer from the above disadvantages.
The above and further objects are achieved by symmetrically securing the throttle body on a spindle rotatably supported crosswise in the intake channel and forming the valve body with an outer circular contour and an inside surface of the wall of the intake channel with an elliptical shape. The throttle valve body thus is a planar disk and in the closed position is inclined with respect to the inside surface of the wall of the intake channel and has opposite edges in peripheral contact with the inside surface.
Because the throttle valve body is cylindrical with a circular periphery and it is planar and because the inside surface of the intake channel has an elliptical contour in the closing region of the valve body, the throttle valve body comes into precise contact with the inside surface of the intake channel and it is possible to secure the throttle valve body to the spindle by an automatic manufacturing process. Adjustment of the throttle valves in a particular direction of rotation is no longer necessary.